1. Field of the Invention
This invention relates to means and a process for reducing exhaust emissions of diesel fuels. More particularly, the invention is concerned with reducing the amount of invisible particulates in diesel engines exhaust emissions. The invention also relates to a method for operating a diesel engine in such a manner that there is produced a minimum of harmful obnoxious exhaust smoke by that engine.
Diesel fuels used in diesel engines give off in the exhaust of the engine particulates which recent tests show to be harmful pollutants. These particulates include not only those that exist as visible smoke when the diesel engine is overloaded or when the engine is worn or dirty, but also those that are invisible and emerge from partly loaded clean diesel engines. The Federal Environmental Protection Agency recently determined that diesel-powered automobiles emit unacceptable high levels of air pollution which must be reduced to ward off a possible health hazard.
Tests of 10 foreign and domestic cars showed many of the vehicles emitted particulate matter, in amounts greatly exceeding the agency's proposed standard for diesel-powered autos.
The proposed standards would allow six-tenths of a gram per mile for 1981 model cars, to be reduced to two-tenths of a gram per mile by the 1983 model year.
2. Description of the Prior Art
The prior art to which this invention relates is aware specifically of coassigned U.S. Pat. No. 2,941,876 which discloses a hydrocarbon fuel composition having incorporated therein a high ester content, high viscosity oxidate capable of performing the dual function of an anticorrosion and a sludge dispersant in the fuel. The oxidates are characterized by a ratio of Neutralization Number to Saponification Number below about 0.25 and an SUS viscosity at 210.degree. F. of at least about 1500 to 20,000.
Also relevant to the present invention are U.S. Pat. Nos. 2,916,454; 3,410,670; 3,413,102; 3,539,312 and 3,499,742. These patents show smoke suppressants are commonly employed in, or added to, diesel fuel oils, particularly when the diesel engines are to be operated in areas of high population density. In general, most common smoke suppressants employed are the organic compounds of barium, particularly the barium carbonate overbased barium sulfonates which are effective for substantially reducing the amount of smoke exhaust from a diesel engine. There are questions concerning the use of barium compounds as smoke suppressants, however, it is well know that some barium compounds are toxic to ingestion by human beings at high dosages. Calcium compounds, particularly calcium carbonate overbased calcium sulfonate, have been proposed to replace the barium carbonate overbased barium compounds in diesel fuels. However, the calcium carbonate overbased calcium sulfonates have not enjoyed any appreciable degree of use because of a number of serious disadvantages connected with their use. The last mentioned patent discloses a smoke inhibited fuel composition comprising a hydrocarbon distillate fuel containing smoke suppressing amounts of a calcium alkyl phenolate or sulfurized calcium alkylphenolate overbased with calcium 2-methoxyethoxide alone or with calcium hydroxide-2-methoxy-ethoxide. None of these patents is concerned with reducing the amount of both soot and invisible particulates emitted by diesel engines.